Reamer roller cone bit with stepped reamer cutter profile

ABSTRACT

A bottom hole assembly including a pilot bit for initially forming an unconfined inner sidewall of a wellbore and a reamer tool above the pilot bit and comprising a first cutter ring to expand the unconfined inner sidewall, and a second cutter ring located above and outwardly of the first cutter ring to expand the unconfined inner sidewall as expanded by the first cutter ring. The reamer tool may further comprise a third cutter ring located above and outwardly of the second cutter ring to expand the unconfined inner sidewall as expanded by the second cutter ring. The first cutter ring may be located on a first roller cone, the second cutter ring may be located on a second roller cone, and the third cutter ring may be located on a third roller cone.

CROSS REFERENCE TO RELATED APPLICATIONS

None.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

REFERENCE TO APPENDIX

Not applicable.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The inventions disclosed and taught herein relate generally to drillingassemblies for drilling wellbores into earth formations; and morespecifically related to reamer tools for such drilling assemblies.

2. Description of the Related Art

U.S. Pat. No. 4,106,577 discloses a “hydromechanical drilling tool whichcombines a high pressure water jet drill with a conventional roller conetype of drilling bit. The high pressure jet serves as a tap drill forcutting a relatively small diameter hole in advance of the conventionalbit. Auxiliary laterally projecting jets also serve to partially cutrock and to remove debris from in front of the bit teeth therebyreducing significantly the thrust loading for driving the bit.”

U.S. Pat. No. 4,141,421 discloses “an under reamer tool for enlarging,scraping or smoothing a well bore. The tool is attached to aconventional drill string above a conventional bit and involves cuttingelements that have retractable cutters arranged for extension from thetool to engage the well bore wall, each cutter, when the drill string isturned, being urged outwardly by centrifugal force until it engages thewell bore wall, continued turning thereafter, pulling that cutter intoits extended cutting attitude, reaming the wall to the desired diameter,cutter retraction involving ceasing turning the drill string and thepulling of the drill string and connected tool from the well bore.During that pulling should the cutter contact a shoe or first reductionof the well bore casing or the wall thereof, it will be urged into astowed attitude recessed within the tool body, the under reamer tool ofthe present invention also incorporating scouring openings provided inthe tool body opposite to the cutter storage areas to pass liquid or airtherethrough from the drill string to purge and clean that area withinthe tool body, allowing the cutter to travel freely therein.”

U.S. Pat. No. 5,497,842 discloses a “reaming apparatus for enlarging aborehole, including a tubular body having one or more longitudinally andgenerally radially extending blades circumferentially spaced thereabout.Each of the blades carries highly exposed cutting elements, on the orderof fifty percent exposure, on its profile substantially all the way tothe gage. At least one of the blades is a primary blade for cutting thefull or drill diameter of the borehole, while one or more others of theblades may be secondary blades which extend a lesser radial distancefrom the body than the primary blade. A secondary blade initially sharesa large portion of the cutting load with the primary blade while theborehole size is in transition between a smaller, pass through diameterand drill diameter. It functions to enhance the rapidity of thetransition while balancing side reaction forces, and reduces vibrationand borehole eccentricity. After drill diameter is reached, cuttingelements on the secondary blade continue to share the cutting load overthe radial distance they extend from the body.”

U.S. Pat. No. 6,439,326 discloses a “drill bit including a roller coneand fixed cutters positioned external to the roller cone and radiallyfrom the bit axis of rotation. The roller cone is located so that adrill diameter of the cone is substantially concentric with an axis ofrotation of the bit. The fixed cutters can be made of tungsten carbide,polycrystalline diamond, boron nitride, or any other superhard material.The fixed cutters are positioned to either maintain the hole diameterdrilled by the roller cone or to drill a larger diameter hole than thehole drilled by the roller cone. The single roller cone may be locatedin the center of a multi-cone bit arrangement or in the center of a PDCbit to assist in drilling the center of a wellbore. The single rollercone may be used to form a bi-center bit in combination with a reamingsection. The single roller cone may also be located on an independentsub that is removably attached to the bit body.”

U.S. Pat. No. 6,729,418 discloses a “back reaming tool is disclosedwhich includes a tool body adapted to be coupled to a drill string, andat least one roller cone rotatably mounted to a leg and having cuttingelements disposed thereon. The leg is removably coupled to the toolbody. The at least one roller cone is open at only one axial endthereof.”

U.S. Pat. No. 7,090,034 discloses “a reamer (100) having at least onejournal body (110) and at least one toroidal cutter body (116). Thetoroidal cutter body (116) has a maximum diameter (MD), an outerperimeter (OP) and a plurality of cutting elements (112, 145, 149) onthe cutting surface (118). The toroidal cutter body is rotatablyattached to the journal (110). When in the installed position, the axisof rotation (RA) of the at least one toroidal cutter body (116)intersects the longitudinal axis of the drill string at an acute angle.”

The inventions disclosed and taught herein are directed to an improvedsystem for drilling and expanding wellbores into earth formations.

BRIEF SUMMARY OF THE INVENTION

In one embodiment, the present invention comprises a bottom holeassembly including a pilot bit for initially forming an unconfined innersidewall of a wellbore and a reamer tool above the pilot bit, the reamertool comprising a first cutter ring configured to expand the unconfinedinner sidewall of the wellbore, and a second cutter ring located aboveand outwardly of the first cutter ring and configured to expand theunconfined inner sidewall as expanded by the first cutter ring. Thereamer tool may further comprise a third cutter ring located above andoutwardly of the second cutter ring and configured to expand theunconfined inner sidewall as expanded by the second cutter ring. Thefirst cutter ring may be located on a first roller cone, the secondcutter ring may be located on a second roller cone, and the third cutterring may be located on a third roller cone. The reamer tool may furthercomprise a fourth cutter ring located on the first roller cone above andoutwardly of the third cutter ring and configured to expand theunconfined inner sidewall as expanded by the third cutter ring, a fifthcutter ring located on the second roller cone above and outwardly of thefourth cutter ring and configured to expand the unconfined innersidewall as expanded by the fourth cutter ring, and a sixth cutter ringlocated on the third roller cone above and outwardly of the fourthcutter ring and configured to expand the unconfined inner sidewall asexpanded by the fifth cutter ring. Each roller cone may include threecutter rows, wherein successive cutter rows are located above andoutwardly of previous cutter rows such that each cutter row engages thewellbore in such a manner as to incrementally expand the wellboreoutwardly. In one embodiment, the wellbore is defined by an unconfinedinner sidewall and successive cutter rows are located above andoutwardly of previous cutter rows such that each cutter row engages thewellbore in such a manner as to incrementally expand the unconfinedinner sidewall outwardly.

In another embodiment, the present invention includes a reamer tool forexpanding a wellbore in an earth formation, the reamer comprising afirst roller cone having a first cutter ring configured to expand anunconfined inner sidewall of the wellbore and a second roller conehaving a second cutter ring located above and outwardly of the firstcutter ring and configured to expand the unconfined inner sidewall ofthe wellbore as expanded by the first cutter ring. The reamer tool mayfurther comprise a third roller cone having a third cutter ring locatedabove and outwardly of the second cutter ring and configured to expandthe unconfined inner sidewall as expanded by the second cutter ring. Thereamer tool may further comprise a fourth cutter ring located on thefirst roller cone above and outwardly of the third cutter ring andconfigured to expand the unconfined inner sidewall as expanded by thethird cutter ring. The reamer tool may further comprise a fifth cutterring located on the second roller cone above and outwardly of the fourthcutter ring and configured to expand the unconfined inner sidewall asexpanded by the fourth cutter ring. The reamer tool may further comprisea sixth cutter ring located on the third roller cone above and outwardlyof the fifth cutter ring and configured to expand the unconfined innersidewall as expanded by the fifth cutter ring.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 illustrates a simplified embodiment of a bottomhole assemblyutilizing certain aspects of the present inventions;

FIG. 2 illustrates a close-up view of a simplified embodiment of aroller cone reamer tool in operation expanding a wellbore, shown withmultiple roller cones and cutters overlain;

FIG. 3 illustrates a particular embodiment of a roller cone utilizingcertain aspects of the present inventions;

FIG. 4 illustrates another particular embodiment of a roller coneutilizing certain aspects of the present inventions;

FIG. 5 illustrates another particular embodiment of a roller coneutilizing certain aspects of the present inventions;

FIG. 6 illustrates another particular embodiment of a roller coneutilizing certain aspects of the present inventions;

FIG. 7 illustrates a composite view of the roller cones of FIGS. 3-6overlain; and

FIG. 8 illustrates another close-up view of a simplified embodiment of aroller cone reamer tool in operation expanding a wellbore, shown withmultiple roller cones and cutters overlain.

DETAILED DESCRIPTION

The Figures described above and the written description of specificstructures and functions below are not presented to limit the scope ofwhat Applicants have invented or the scope of the appended claims.Rather, the Figures and written description are provided to teach anyperson skilled in the art to make and use the inventions for whichpatent protection is sought. Those skilled in the art will appreciatethat not all features of a commercial embodiment of the inventions aredescribed or shown for the sake of clarity and understanding. Persons ofskill in this art will also appreciate that the development of an actualcommercial embodiment incorporating aspects of the present inventionswill require numerous implementation-specific decisions to achieve thedeveloper's ultimate goal for the commercial embodiment. Suchimplementation-specific decisions may include, and likely are notlimited to, compliance with system-related, business-related,government-related and other constraints, which may vary by specificimplementation, location and from time to time. While a developer'sefforts might be complex and time-consuming in an absolute sense, suchefforts would be, nevertheless, a routine undertaking for those of skillthis art having benefit of this disclosure. It must be understood thatthe inventions disclosed and taught herein are susceptible to numerousand various modifications and alternative forms. Lastly, the use of asingular term, such as, but not limited to, “a,” is not intended aslimiting of the number of items. Also, the use of relational terms, suchas, but not limited to, “top,” “bottom,” “left,” “right,” “upper,”“lower,” “down,” “up,” “side,” and the like are used in the writtendescription for clarity in specific reference to the Figures and are notintended to limit the scope of the invention or the appended claims.

Applicants have created a bottom hole assembly including a pilot bit forinitially forming an unconfined inner sidewall of a wellbore and areamer tool above the pilot bit and comprising a first cutter ring toexpand the unconfined inner sidewall and a second cutter ring locatedabove and outwardly of the first cutter ring to expand the unconfinedinner sidewall as expanded by the first cutter ring. The reamer tool mayfurther comprise a third cutter ring located above and outwardly of thesecond cutter ring to expand the unconfined inner sidewall as expandedby the second cutter ring. The first cutter ring may be located on afirst roller cone, the second cutter ring may be located on a secondroller cone, and the third cutter ring may be located on a third rollercone.

FIG. 1 is an illustration of a bottomhole assembly 10 in which thereamer tool 100 of the present invention may be employed. The bottomholeassembly may be similar to that shown and described in U.S. Pat. No.5,497,842, incorporated herein by specific reference. The bottomholeassembly 10 may include one or more drill collars 12 suspended from adistal end of a drill string extending to the rig floor at the surface.An optional pass through stabilizer 14 may be secured to the drillcollar 12. The stabilizer 14 may be sized equal to or slightly smallerthan the pass through diameter of the bottomhole assembly 10, which maybe defined as the smallest diameter borehole through which the assemblymay move longitudinally. Another drill collar 16 (or other drill stringelement such as an measurement while drilling (MWD) tool housing or ponycollar) may be secured to the bottom of the stabilizer 14, below whichthe reamer tool 100 according to the present invention is secured via atool joint 18, which may be an American Petroleum Institute (API) joint.More specifically, in one embodiment, a 7⅝ inch API pin connector islocated at the top of the reamer tool 100. Another API joint 22 islocated at the bottom of the reamer tool 100. More specifically, in oneembodiment, a 6⅝ inch API box connector is located at the bottom of thereamer tool 100. An upper pilot stabilizer 24, preferably secured to thereamer tool 100, is of an O.D. equal to or slightly smaller than that ofa pilot bit 30 at the bottom of the assembly 10. Yet another, smallerdiameter drill collar 26 may be secured to the lower end of the upperpilot stabilizer 24, followed by a lower pilot stabilizer 28 to which issecured the pilot bit 30. The pilot bit 30 may be either a rotary dragbit or a tri-cone, so-called “rock bit”. The bottomhole assembly 10 asdescribed is exemplary only, it being appreciated by those of ordinaryskill in the art that many other assemblies and variations may beemployed.

The bottomhole assembly 10 creates and expands a borehole, or wellbore,in an earth formation. The borehole preferably includes an initial innersidewall 40 created by the pilot bit 30. The borehole also preferablyincludes a final inner sidewall 42 created by the reamer tool 100, aswill be discussed in greater detail below. Between the initial innersidewall 40 and the final inner sidewall 42, there is a working surface44 of the reamer tool 100. In one embodiment of the reamer tool 100,this working surface 44 is a generally conical surface sloped upwardlyand outwardly from the initial inner sidewall 40 to the final innersidewall 42. As can be seen in FIG. 2 and as will be discussed ingreater detail below, while the working surface 44 is generally linear,the working surface 44 is actually discontinuous and comprised of aseries of steps, stepping up and outward from the initial inner sidewall40 to the final inner sidewall 42. Where the working surface 44 meetsthe initial inner sidewall 40, the wellbore forms an inner corner 46. Itcan be seen that the initial inner sidewall 40, the final inner sidewall42, the working surface 44, and the inner corner 46 are allunconstrained, or unconfined, toward the interior of the wellbore. Aswill be discussed in greater detail below, the reamer tool 100 of thepresent invention takes advantage of this unconfined characteristic.

In one preferred embodiment, as shown in FIG. 3, FIG. 4, FIG. 5, andFIG. 6, the reamer tool 100 includes four roller cones 102,104,106,108,each with a plurality of rings, or rows, of cutters 110. In anotherpreferred embodiment, the reamer tool 100 includes three roller cones102,104,106, each with a plurality of rings, rows, of cutters 110. Inany case, the reamer tool 100 is expected to have between two and eightroller cones. FIG. 7 shows how, in actual use, the roller cones102,104,106,108 effectively overlap, such that the cutters 110 of theroller cones 102,140,106,108 form a cutting profile 112, which engagesand therefore effectively defines, or creates, the working surface 44 ofthe wellbore.

The roller cones 102,104,106,108 are angled such that the cutters 110successively engage the earth formation upwardly and outwardly. It canbe appreciated that the pilot bit 30 has initiated the borehole, orwellbore, thereby creating the initial unconfined inner sidewall 40 ofthe wellbore. An uppermost edge of the initial unconfined inner sidewallforms the unconfined inner corner 46 a of the wellbore. Beingunconfined, open to the initial inner sidewall 40 formed by the pilotbit 30 below the reamer tool 100, this inner corner 46 a is lessresistant to excavation. This is due to the fact that the inner corner46 a is only confined, or constrained, outwardly. In other words, theinner corner 46 a is unconfined, or constrained inwardly, as the earthformation inwardly has already been removed by the pilot bit 30.

Therefore, successive rows, or rings, of the cutters 110 preferablyengage the unconfined portions of the wellbore, successively expandingthe wellbore outwardly. More specifically, referring also to FIG. 8, afirst row 114 a of cutters 110 engages the unconfined inner corner 46 aof the wellbore, thereby expanding the initial inner sidewall 40 of thewellbore outwardly. As the bottomhole assembly 10 is lowered into thewellbore and the first row 114 a of cutters 110 engages and excavatesthis unconfined inner corner 46 a, the cutters 110 move the unconfinedinner corner 46 a downwardly. The first row 114 a of cutters 110 alsocreates a first step 48 a in the wellbore. This first step 48 a beginsat the unconfined inner corner 46 a of the wellbore and extendsoutwardly therefrom. The first step 48 a also extends upwardly slightly,forming a second unconfined corner 46 b of the wellbore.

Next, a second row 114 b of cutters 110 engages the second unconfinedcorner 46 b of the wellbore, thereby successively expanding the initialinner sidewall 40 of the wellbore outwardly. As the bottomhole assembly10 is lowered into the wellbore and the second row 114 b of cutters 110engages and excavates this second unconfined corner 46 b, the cutters110 move the second unconfined corner 46 b downwardly. The second row114 b of cutters 110 also creates a second step 48 b in the wellbore.This second step 48 b begins at the second unconfined corner 46 b of thewellbore and extends outwardly therefrom. The second step 48 b alsoextends upwardly slightly, forming a third unconfined corner 46 c of thewellbore.

Next, a third row 114 c of cutters 110 engages the third unconfinedcorner 46 c of the wellbore, thereby successively expanding the initialinner sidewall 40 of the wellbore outwardly. As the bottomhole assembly10 is lowered into the wellbore and the third row 114 c of cutters 110engages and excavates this third unconfined corner 46 c, the cutters 110move the third unconfined corner 46 c downwardly. The third row 114 c ofcutters 110 also creates a third step 48 c in the wellbore. This thirdstep 48 c begins at the third unconfined corner 46 c of the wellbore andextends outwardly therefrom. The third step 48 c also extends upwardlyslightly, forming a fourth unconfined corner 46 d of the wellbore.

Next, a fourth row 114 d of cutters 110 engages the fourth unconfinedcorner 46 d of the wellbore, thereby successively expanding the initialinner sidewall 40 of the wellbore outwardly. As the bottomhole assembly10 is lowered into the wellbore and the fourth row 114 d of cutters 110engages and excavates this fourth unconfined corner 46 d, the cutters110 move the fourth unconfined corner 46 d downwardly. The fourth row114 d of cutters 110 also creates a fourth step 48 d in the wellbore.This fourth step 48 d begins at the fourth unconfined corner 46 d of thewellbore and extends outwardly therefrom. The fourth step 48 d alsoextends upwardly slightly, forming a fifth unconfined corner 46 e of thewellbore.

Next, a fifth row 114 e of cutters 110 engages the fifth unconfinedcorner 46 e of the wellbore, thereby successively expanding the initialinner sidewall 40 of the wellbore outwardly. As the bottomhole assembly10 is lowered into the wellbore and the fifth row 114 e of cutters 110engages and excavates this fifth unconfined corner 46 e, the cutters 110move the fifth unconfined corner 46 e downwardly. The fifth row 114 e ofcutters 110 also creates a fifth step 48 e in the wellbore. This fifthstep 48 e begins at the fifth unconfined corner 46 e of the wellbore andextends outwardly therefrom. The fifth step 48 e also extends upwardlyslightly, forming a sixth unconfined corner 46 f of the wellbore.

Next, a sixth row 114 f of cutters 110 engages the sixth unconfinedcorner 46 f of the wellbore, thereby successively expanding the initialinner sidewall 40 of the wellbore outwardly. As the bottomhole assembly10 is lowered into the wellbore and the sixth row 114 f of cutters 110engages and excavates this sixth unconfined corner 46 f, the cutters 110move the sixth unconfined corner 46 f downwardly. The sixth row 114 f ofcutters 110 also creates a sixth step 48 f in the wellbore. This sixthstep 48 f begins at the sixth unconfined corner 46 f of the wellbore andextends outwardly therefrom. The sixth step 48 f also extends upwardlyslightly, forming a seventh unconfined corner 46 g of the wellbore.

Next, a seventh row 114 g of cutters 110 engages the seventh unconfinedcorner 46 g of the wellbore, thereby successively expanding the initialinner sidewall 40 of the wellbore outwardly. As the bottomhole assembly10 is lowered into the wellbore and the seventh row 114 g of cutters 110engages and excavates this seventh unconfined corner 46 g, the cutters110 move the seventh unconfined corner 46 g downwardly. The seventh row114 g of cutters 110 also creates a seventh step 48 g in the wellbore.This seventh step 48 g begins at the seventh unconfined corner 46 g ofthe wellbore and extends outwardly therefrom. The seventh step 48 g alsoextends upwardly slightly, forming an eighth unconfined corner 46 h ofthe wellbore.

Next, an eighth row 114 h of cutters 110 engages the eighth unconfinedcorner 46 h of the wellbore, thereby successively expanding the initialinner sidewall 40 of the wellbore outwardly. As the bottomhole assembly10 is lowered into the wellbore and the eighth row 114 h of cutters 110engages and excavates this eighth unconfined corner 46 h, the cutters110 move the eighth unconfined corner 46 h downwardly. The eighth row114 h of cutters 110 also creates an eighth step 48 h in the wellbore.This eighth step 48 h begins at the eighth unconfined corner 46 h of thewellbore and extends outwardly therefrom. The eighth step 48 h alsoextends upwardly slightly, forming a ninth unconfined corner 46 i of thewellbore.

Next, a ninth row 114 i of cutters 110 engages the ninth unconfinedcorner 46 i of the wellbore, thereby successively expanding the initialinner sidewall 40 of the wellbore outwardly. As the bottomhole assembly10 is lowered into the wellbore and the ninth row 114 i of cutters 110engages and excavates this ninth unconfined corner 46 i, the cutters 110move the ninth unconfined corner 46 i downwardly. The ninth row 114 i ofcutters 110 also creates a ninth step 48 i in the wellbore. This ninthstep 48 i begins at the ninth unconfined corner 46 i of the wellbore andextends outwardly therefrom. The ninth step 48 i also extends upwardlyslightly, forming a tenth unconfined corner 46 j of the wellbore.

Next, a tenth row 114 j of cutters 110 engages the tenth unconfinedcorner 46 j of the wellbore, thereby successively expanding the initialinner sidewall 40 of the wellbore outwardly. As the bottomhole assembly10 is lowered into the wellbore and the tenth row 114 j of cutters 110engages and excavates this tenth unconfined corner 46 j, the cutters 110move the tenth unconfined corner 46 j downwardly. The tenth row 114 j ofcutters 110 also creates a tenth step 48 j in the wellbore. This tenthstep 48 j begins at the tenth unconfined corner 46 j of the wellbore andextends outwardly therefrom. The tenth step 48 j also extends upwardlyslightly, forming an eleventh unconfined corner 46 k of the wellbore.

Next, an eleventh row 114 k of cutters 110 engages the eleventhunconfined corner 46 k of the wellbore, thereby successively expandingthe initial inner sidewall 40 of the wellbore outwardly. As thebottomhole assembly 10 is lowered into the wellbore and the eleventh row114 k of cutters 110 engages and excavates this eleventh unconfinedcorner 46 k, the cutters 110 move the eleventh unconfined corner 46 kdownwardly. The eleventh row 114 k of cutters 110 also creates aneleventh step 48 k in the wellbore. This eleventh step 48 k begins atthe eleventh unconfined corner 46 k of the wellbore and extendsoutwardly therefrom. The eleventh step 48 k also extends upwardlyslightly, forming a twelfth unconfined corner 46 l of the wellbore.

Next, a twelfth row 114 l of cutters 110 engages the twelfth unconfinedcorner 46 l of the wellbore, thereby successively expanding the initialinner sidewall 40 of the wellbore outwardly. As the bottomhole assembly10 is lowered into the wellbore and the twelfth row 114 l of cutters 110engages and excavates this twelfth unconfined corner 46 l, the cutters110 move the twelfth unconfined corner 46 l downwardly. The twelfth row114 l of cutters 110 also creates a twelfth step 48 l in the wellbore.This twelfth step 48 l begins at the twelfth unconfined corner 46 l ofthe wellbore and extends outwardly therefrom. In one embodiment of thereamer tool 100, the twelfth step 48 l terminates in the final innersidewall 42 of the wellbore.

The rows 114 a-114 l of cutters 110 are preferably dispersed across theroller cones 102-108. In the embodiment of the reamer tool having fourroller cones 102-108, each roller cones preferably has three of the rows114 a-114 l of cutters 110. More specifically, in this particularembodiment, the first roller cone 102 preferably includes the first row114 a, the fifth row 114 e, and the ninth row 114 i of cutters 110. Inthis particular embodiment, the second roller cone 104 preferablyincludes the second row 114 b, the sixth row 114 f, and the tenth row114 j of cutters 110. In this particular embodiment, the third rollercone 106 preferably includes the third row 114 c, the seventh row 114 g,and the eleventh row 114 k of cutters 110. In this particularembodiment, the fourth roller cone 108 preferably includes the fourthrow 114 d, the eighth row 114 h, and the twelfth row 114 l of cutters110.

In the embodiment of the reamer tool having three roller cones 102-106,each roller cones preferably has four of the rows 114 a-114 l of cutters110. More specifically, in this particular embodiment, the first rollercone 102 preferably includes the first row 114 a, the fourth row 114 d,the seventh row 114 g, and the tenth row 114 j of cutters 110. In thisparticular embodiment, the second roller cone 104 preferably includesthe second row 114 b, the fifth row 114 e, the eighth row 114 h, and theeleventh row 114 k of cutters 110. In this particular embodiment, thethird roller cone 106 preferably includes the third row 114 c, the sixthrow 114 f, the ninth row 114 i, and the twelfth row 114 l of cutters110.

In both embodiments, dispersing the rows 114 a-114 l of cutters 110across multiple cones, provides adequate spacing between the rows 114a-114 l, while still providing an overlapping cutter profile 112,thereby allowing shavings, or cuttings, to be removed by drilling fluidor other processes known in the art. In other words, the cutter profile112 engages the working surface 44 with overlapping cutters 110, therows 114 a-114 l of cutters 110 overlapping from one roller cone to thenext. At the same time, however, the rows 114 a-114 l on any one rollercone 102-108 are adequately spaced to allow the cuttings to be removed.The dispersion, distribution, and/or spacing of the cutters 110themselves, as well as the rows 114 a-114 l of cutters 110, allows theroller cones 102-108 to freely rotate without the cutters 110 cominginto contact with one another.

In one embodiment of the reamer tool 100, dispersing the rows 114 a-114l of cutters 110 across multiple roller cones allows the cutter profile112 to engage the working surface 44 with overlapping cutters 110,without the cutters 110 from one roller cone meshing with the cutters110 from another roller cone. This allows the roller cones102,104,106,108 to rotate independently of each other. Spacing of theroller cones 102,104,106,108, themselves, around the reamer tool 100,may aid in separating the cutters 110 from different roller cones.

In any case, it can be seen that successive rows 114 a-114 l of cutters110 are located above and outwardly of previous cutter rows such thateach cutter row engages the wellbore in such a manner as toincrementally expand the wellbore outwardly, as the bottomhole assembly10 is lowered into the wellbore. More specifically, successive rows 114a-114 l of cutters 110 are located above and outwardly of previouscutter rows such that each cutter row engages the wellbore in such amanner as to incrementally expand the unconfined inner sidewall 40outwardly. Still more specifically, in one embodiment, a first cutterring, or row, 114 a is configured to expand the unconfined innersidewall 40 of the wellbore, a second cutter ring 114 b is located aboveand outwardly of the first cutter ring 114 a and configured to expandthe unconfined inner sidewall 40 as expanded by the first cutter ring114 a, and a third cutter ring 114 c is located above and outwardly ofthe second cutter ring and configured to expand the unconfined innersidewall as expanded by the second cutter ring.

Other and further embodiments utilizing one or more aspects of theinventions described above can be devised without departing from thespirit of Applicant's invention. For example, just as more or fewerroller cones may be used, more or fewer rows of cutters can be used oneach roller cone. While the roller cones are described as having equalnumbers of rows of cutters, roller cones having different numbers ofrows of cutters could be used in some embodiments. Further, in someembodiments, one or more of the cutter rings, may be embodied as acutter disk, a serrated disk, a row or ring of milled and hardfacedteeth, and/or a row of tungsten carbide inserts.

Additionally, or alternatively, in one embodiment, each outer-most rowof cutters, or cutter ring, on each roller cone 102,104,106,108 combineto contribute to the final inner sidewall 42 of the wellbore. Forexample, in an embodiment with four roller cones 102,104,106,108, theninth row 114 i of cutters 110 on the first roller cone 102, the tenthrow 114 j of cutters 110 on the second roller cone 104, the eleventh row114 k of cutters 110 on the third roller cone 106, and the twelfth row114 l of cutters 110 on the fourth roller cone 108 all contribute to thefinal inner sidewall 42 of the wellbore. In this case, the ninth row 114i of cutters 110 may be longer and/or otherwise configured differentlyfrom the twelfth row 114 l of cutters 110. In other embodiments, one,two, three, or more outer-most cutter rings contribute to the finalinner sidewall 42 of the wellbore. In any case, by having multiplecutter rings contribute, this provides a smoother, more uniform, andmore consistently sized and shaped final inner sidewall 42.

The order of steps can occur in a variety of sequences unless otherwisespecifically limited. The various steps described herein can be combinedwith other steps, interlineated with the stated steps, and/or split intomultiple steps. Similarly, elements have been described functionally andcan be embodied as separate components or can be combined intocomponents having multiple functions. Finally, the various methods andembodiments of the reamer tool 100 can be included in combination witheach other to produce variations of the disclosed methods andembodiments. Discussion of singular elements can include plural elementsand vice-versa. For example, in some embodiments, rather than one ofeach individual cone 102,104,106,108 described above, there may be two,spaced at approximately 180 degrees, three spaced at approximately 120degrees, four spaced at approximately 90 degrees, or more, for each conedescribed above. More specifically, there may be two or more firstroller cones, configured and performing as described above, but spaced180 degrees across the reamer tool 100.

As discussed above, it is anticipated that the roller cones will besubstantially uniformly spaced around the reamer tool 100. However, inone embodiment, four roller cones are spaced at 90 degrees, 90 degrees,100 degrees, and 80 degrees, on center. Therefore, the roller cones maybe offset five, ten, fifteen, or twenty degrees, or some included range,off otherwise uniform spacing. This spacing applies to embodimentshaving singular and/or multiple individual first, second, third, and/orfourth roller cones 102,104,106,108.

The inventions have been described in the context of preferred and otherembodiments and not every embodiment of the invention has beendescribed. Obvious modifications and alterations to the describedembodiments are available to those of ordinary skill in the art. Thedisclosed and undisclosed embodiments are not intended to limit orrestrict the scope or applicability of the invention conceived of by theApplicants, but rather, in conformity with the patent laws, Applicantsintend to fully protect all such modifications and improvements thatcome within the scope or range of equivalent of the following claims.

1. A reamer tool for expanding a wellbore in an earth formation, thereamer tool comprising: a first roller cone having a first cutter ringconfigured to expand an unconfined inner sidewall of the wellbore; and asecond roller cone having a second cutter ring located above andoutwardly of the first cutter ring and configured to expand theunconfined inner sidewall of the wellbore as expanded by the firstcutter ring.
 2. The reamer tool as set forth in claim 1, furthercomprising a third roller cone having a third cutter ring located aboveand outwardly of the second cutter ring and configured to expand theunconfined inner sidewall as expanded by the second cutter ring.
 3. Thereamer tool as set forth in claim 2, further comprising a fourth cutterring located on the first roller cone above and outwardly of the thirdcutter ring and configured to expand the unconfined inner sidewall asexpanded by the third cutter ring.
 4. The reamer tool as set forth inclaim 3, further comprising a fifth cutter ring located on the secondroller cone above and outwardly of the fourth cutter ring and configuredto expand the unconfined inner sidewall as expanded by the fourth cutterring.
 5. The reamer tool as set forth in claim 4, further comprising asixth cutter ring located on the third roller cone above and outwardlyof the fifth cutter ring and configured to expand the unconfined innersidewall as expanded by the fifth cutter ring.
 6. A bottom hole assemblycomprising: a pilot bit for initially forming an unconfined innersidewall of a wellbore; and a reamer tool above the pilot bit, thereamer tool including a first cutter ring configured to expand theunconfined inner sidewall of the wellbore, a second cutter ring locatedabove and outwardly of the first cutter ring and configured to expandthe unconfined inner sidewall as expanded by the first cutter ring, anda third cutter ring located above and outwardly of the second cutterring and configured to expand the unconfined inner sidewall as expandedby the second cutter ring.
 7. The bottom hole assembly as set forth inclaim 6, the reamer tool further comprising first, second and thirdroller cones.
 8. The bottom hole assembly as set forth in claim 7,wherein the first cutter ring is located on the first roller cone, thesecond cutter ring located on the second roller cone, and the thirdcutter ring is located on the third roller cone.
 9. The bottom holeassembly as set forth in claim 8, further comprising a fourth cutterring located on the first roller cone above and outwardly of the thirdcutter ring and configured to expand the unconfined inner sidewall asexpanded by the third cutter ring; a fifth cutter ring located on thesecond roller cone above and outwardly of the fourth cutter ring andconfigured to expand the unconfined inner sidewall as expanded by thefourth cutter ring; and a sixth cutter ring located on the third rollercone above and outwardly of the fourth cutter ring and configured toexpand the unconfined inner sidewall as expanded by the fifth cutterring.
 10. The bottom hole assembly as set forth in claim 9, wherein eachroller cone includes at least three cutter rows, wherein successivecutter rows are located above and outwardly of previous cutter rows suchthat each cutter row engages the wellbore in such a manner as toincrementally expand the wellbore outwardly.
 11. The bottom holeassembly as set forth in claim 9, wherein the wellbore is defined by anunconfined inner sidewall and successive cutter rows are located aboveand outwardly of previous cutter rows such that each cutter row engagesthe wellbore in such a manner as to incrementally expand the unconfinedinner sidewall outwardly.
 12. A method of expanding a wellbore using areamer tool comprising a plurality of cutter rows mounted on a pluralityof roller cones, the method comprising the steps of: engaging, with afirst cutter row on a first roller cone, an unconfined inner sidewall ofthe wellbore, thereby expanding the wellbore outwardly; and engaging,with a second cutter row located on a second roller cone above andoutwardly of the first cutter row, the unconfined inner sidewall of thewellbore as expanded by the first cutter row, thereby further expandingthe wellbore outwardly.
 13. The method as set forth in claim 12, furtherincluding the step of engaging, with a third cutter row located on athird roller cone above and outwardly of the second cutter row, theunconfined inner sidewall of the wellbore as expanded by the secondcutter row, thereby further expanding the wellbore outwardly.
 14. Themethod as set forth in claim 13, further including the steps ofengaging, with a fourth cutter row located on the first roller coneabove and outwardly of the third cutter row, the unconfined innersidewall of the wellbore as expanded by the third cutter row; engaging,with a fifth cutter row located on the second roller cone above andoutwardly of the fourth cutter row, the unconfined inner sidewall of thewellbore as expanded by the fourth cutter row; and engaging, with asixth cutter row located on the third roller cone above and outwardly ofthe fifth cutter row, the unconfined inner sidewall of the wellbore asexpanded by the fifth cutter row.
 15. The method as set forth in claim12, wherein the reamer expands the wellbore outwardly from theunconfined inner sidewall of the wellbore and the reamer tool is loweredin the wellbore.
 16. The method as set forth in claim 12, wherein thewellbore is defined by an initial inner sidewall formed by a pilot bitbelow the reamer tool, a first step formed by the first cutter rowadjacent the initial inner sidewall, a second step formed by the secondcutter row above and outward of the first step, and a final innersidewall formed by the reamer tool.